1. Field of the Invention
The present invention relates to a regulating dispenser, for example for seeds. More particularly it relates to a regulating dispenser comprising a hopper, a movable surface for withdrawing material from the bottom of the hopper to the outside thereof and means for regulating the delivery rate.
2. Description of the Prior Art
Mostly, these dispensers are of the type shown in the accompanying drawings (FIGS. 1 and 1a), in which a grooved cylinder 1 is rotated in a slot 1' -- formed in the lower part of a fixed wall 2 of a hopper or dispensing box 2' -- so that the grooves 5 scoop from the mass 4 contained in the box and withdraw a predetermined amount of the material in the form of a layer, a valve 3 displaceable in its plane, for example parallel to said fixed wall, enabling the thickness e of the layer (FIG. 1b) to be adjusted as desired.
Such an arrangement is to be found, for example, in British patent specification No. 7121 AD 1913 and DT Pat. No. 235,688.
When small delivery rates are desired with a large take-up surface for the material, it is advantageous to avoid arching and to have a large surface at the base of the hopper, which reduces the height thereof, to replace the cylinder with continuous grooves of FIG. 1 by aligned pinion wheels forming a smooth part between recesses and to scrape off the material which could be entrained on this smooth part.
A construction of this type is the subject of U.S. Pat. No. 3,387,751, relating to a regulating dispenser comprising a recessed cylinder and a fixed scraper. To vary the delivery rate, the cylinder is moved along its axis so that a recessed section comes more or less to face an outlet orifice. Another solution, which has the same drawbacks, is shown in FIGS. 2 and 2a. The fixed wall 2 scrapes off the material 4 between the recesses: the fixed wall 2 forming part of the dispensing box, there is necessarily play between the pinion cylinder 1 and this wall and on account of this, a lack of sealing; as a result, the particles of the material to be dispensed slip between the cylinder 1 and the wall 2 and wear said wall 2 and cylinder 1, which become scored, resulting in increases in the flow rate of the dispensed material.
Lastly, dispensers are known in which the withdrawal of the material from the hopper is effected by a conveyor belt associated with an adjustable slot, for example those which are the subject of French Pat. Nos. 771,156 and 1,137,836 in the name of Applicant. These arrangements have the same drawbacks as the foregoing ones.